A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

A unique geological area spiked with wind-carved rocks that resemble teepees.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

This tea house was a hand-built gift from Boulder's sister city in Tajikstan.

The scene of one of the darkest moments in American labor history has been left essentially untouched since the tragedy.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Dramatic river bend surrounds a natural red-rocked pedestal.

Legends surround this jagged rock formation in the New Mexico desert.

Shoreline strewn with the remains of ghostly fallen trees.

No one knows how this Pacific Northwest spruce tree came to have so many trunks.

This extravagant Art Nouveau rest stop features a million-dollar view of the Columbia River.

The magic's in the hole!

Stroll through a wonderland of stupendous moss-covered trees.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

The longest continuous lava tube in Oregon.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

The final resting place of two (or three) presidents, one vampire, and 18,000 Confederate soldiers.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?